/*
    This file is part of the iText (R) project.
    Copyright (c) 1998-2022 iText Group NV
    Authors: iText Software.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License version 3
    as published by the Free Software Foundation with the addition of the
    following permission added to Section 15 as permitted in Section 7(a):
    FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
    ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
    OF THIRD PARTY RIGHTS
    
    This program is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    or FITNESS FOR A PARTICULAR PURPOSE.
    See the GNU Affero General Public License for more details.
    You should have received a copy of the GNU Affero General Public License
    along with this program; if not, see http://www.gnu.org/licenses or write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA, 02110-1301 USA, or download the license from the following URL:
    http://itextpdf.com/terms-of-use/
    
    The interactive user interfaces in modified source and object code versions
    of this program must display Appropriate Legal Notices, as required under
    Section 5 of the GNU Affero General Public License.
    
    In accordance with Section 7(b) of the GNU Affero General Public License,
    a covered work must retain the producer line in every PDF that is created
    or manipulated using iText.
    
    You can be released from the requirements of the license by purchasing
    a commercial license. Buying such a license is mandatory as soon as you
    develop commercial activities involving the iText software without
    disclosing the source code of your own applications.
    These activities include: offering paid services to customers as an ASP,
    serving PDFs on the fly in a web application, shipping iText with a closed
    source product.
    
    For more information, please contact iText Software Corp. at this
    address: sales@itextpdf.com
 */
using System;
using System.Text;
/**
 *
 */
namespace iTextSharp.text.xml {

    /**
     * Contains utility methods for XML.
     * @author Balder
     * @since 5.0.6
     *
     */
    public static class XMLUtil {

         /**
         * Escapes a string with the appropriated XML codes.
         * @param s the string to be escaped
         * @param onlyASCII codes above 127 will always be escaped with &amp;#nn; if <CODE>true</CODE>
         * @return the escaped string
         * @since 5.0.6
         */
        public static String EscapeXML(String s, bool onlyASCII) {
            char[] cc = s.ToCharArray();
            int len = cc.Length;
            StringBuilder sb = new StringBuilder();
            for (int k = 0; k < len; ++k) {
                int c = cc[k];
                switch (c) {
                    case '<':
                        sb.Append("&lt;");
                        break;
                    case '>':
                        sb.Append("&gt;");
                        break;
                    case '&':
                        sb.Append("&amp;");
                        break;
                    case '"':
                        sb.Append("&quot;");
                        break;
                    case '\'':
                        sb.Append("&apos;");
                        break;
                    default:
                        if (IsValidCharacterValue(c)) {
                            if (onlyASCII && c > 127)
                                sb.Append("&#").Append(c).Append(';');
                            else
                                sb.Append((char)c);
                        }
                        break;
                }
            }
            return sb.ToString();
        }

        /**
         * Unescapes a String, replacing &#nn;, &lt;, &gt;, &amp;, &quot;,
         * and &apos to the corresponding characters.
         * @param s a String with entities
         * @return the unescaped string
         */
        public static String UnescapeXML(String s) {
            char[] cc = s.ToCharArray();
            int len = cc.Length;
            StringBuilder sb = new StringBuilder();
            int pos;
            String esc;
            for (int i = 0; i < len; i++) {
                int c = cc[i];
                if (c == '&') {
                    pos = FindInArray(';', cc, i + 3);
                    if (pos > -1) {
                        esc = new String(cc, i + 1, pos - i - 1);
                        if (esc.StartsWith("#")) {
                            esc = esc.Substring(1);
                            if (IsValidCharacterValue(esc)) {
                                c = (char)int.Parse(esc);
                                i = pos;
                            } else {
                                i = pos;
                                continue;
                            }
                        }
                        else {
                            int tmp = Unescape(esc);
                            if (tmp > 0) {
                                c = tmp;
                                i = pos;
                            }
                        }
                    }
                }
                sb.Append((char)c);
            }
            return sb.ToString();
        }
     
        /**
         * Unescapes 'lt', 'gt', 'apos', 'quote' and 'amp' to the
         * corresponding character values.
         * @param   s   a string representing a character
         * @return  a character value
         */
        public static int Unescape(String s) {
            if ("apos".Equals(s))
                return '\'';
            if ("quot".Equals(s))
                return '"';
            if ("lt".Equals(s))
                return '<';
            if ("gt".Equals(s))
                return '>';
            if ("amp".Equals(s))
                return '&';
            return -1;
        }
        
        /**
         * Checks if a character value should be escaped/unescaped.
         * @param   s   the String representation of an integer
         * @return  true if it's OK to escape or unescape this value 
         */
        public static bool IsValidCharacterValue(String s) {
            try {
                int i = int.Parse(s);
                return IsValidCharacterValue(i);
            }
            catch {
                return false;
            }
        }
        
        /**
         * Checks if a character value should be escaped/unescaped.
         * @param   c   a character value
         * @return  true if it's OK to escape or unescape this value 
         */
        public static bool IsValidCharacterValue(int c) {
            return (c == 0x9 || c == 0xA || c == 0xD
                    || c >= 0x20 && c <= 0xD7FF
                    || c >= 0xE000 && c <= 0xFFFD
                    || c >= 0x10000 && c <= 0x10FFFF);
        }
        
        /**
         * Looks for a character in a character array, starting from a certain position
         * @param needle    the character you're looking for
         * @param haystack  the character array
         * @param start     the start position
         * @return  the position where the character was found, or -1 if it wasn't found.
         */
        public static int FindInArray(char needle, char[] haystack, int start) {
            for (int i = start; i < haystack.Length; i++) {
                if (haystack[i] == ';')
                    return i;
            }
            return -1;
        }

        /**
         * Returns the IANA encoding name that is auto-detected from
         * the bytes specified, with the endian-ness of that encoding where appropriate.
         * (method found in org.apache.xerces.impl.XMLEntityManager, originally published
         * by the Apache Software Foundation under the Apache Software License; now being
         * used in iText under the MPL)
         * @param b4    The first four bytes of the input.
         * @return an IANA-encoding string
         * @since 5.0.6
         */
        public static String GetEncodingName(byte[] b4) {

            // UTF-16, with BOM
            int b0 = b4[0] & 0xFF;
            int b1 = b4[1] & 0xFF;
            if (b0 == 0xFE && b1 == 0xFF) {
                // UTF-16, big-endian
                return "UTF-16BE";
            }
            if (b0 == 0xFF && b1 == 0xFE) {
                // UTF-16, little-endian
                return "UTF-16LE";
            }

            // UTF-8 with a BOM
            int b2 = b4[2] & 0xFF;
            if (b0 == 0xEF && b1 == 0xBB && b2 == 0xBF) {
                return "UTF-8";
            }

            // other encodings
            int b3 = b4[3] & 0xFF;
            if (b0 == 0x00 && b1 == 0x00 && b2 == 0x00 && b3 == 0x3C) {
                // UCS-4, big endian (1234)
                return "ISO-10646-UCS-4";
            }
            if (b0 == 0x3C && b1 == 0x00 && b2 == 0x00 && b3 == 0x00) {
                // UCS-4, little endian (4321)
                return "ISO-10646-UCS-4";
            }
            if (b0 == 0x00 && b1 == 0x00 && b2 == 0x3C && b3 == 0x00) {
                // UCS-4, unusual octet order (2143)
                // REVISIT: What should this be?
                return "ISO-10646-UCS-4";
            }
            if (b0 == 0x00 && b1 == 0x3C && b2 == 0x00 && b3 == 0x00) {
                // UCS-4, unusual octet order (3412)
                // REVISIT: What should this be?
                return "ISO-10646-UCS-4";
            }
            if (b0 == 0x00 && b1 == 0x3C && b2 == 0x00 && b3 == 0x3F) {
                // UTF-16, big-endian, no BOM
                // (or could turn out to be UCS-2...
                // REVISIT: What should this be?
                return "UTF-16BE";
            }
            if (b0 == 0x3C && b1 == 0x00 && b2 == 0x3F && b3 == 0x00) {
                // UTF-16, little-endian, no BOM
                // (or could turn out to be UCS-2...
                return "UTF-16LE";
            }
            if (b0 == 0x4C && b1 == 0x6F && b2 == 0xA7 && b3 == 0x94) {
                // EBCDIC
                // a la xerces1, return CP037 instead of EBCDIC here
                return "CP037";
            }

            // default encoding
            return "UTF-8";
        }
    }
}
